20
XX
10100
The number 20 — factors and divisors
Abundant
20 = 2² × 5. It has 6 divisors, adding up to 42.
Its divisors, itself excluded, add up to more than the number.
Laid out as dots
It fits as 4 × 5. The more divisors, the closer to a square.
- Prime factors
- 2² × 5
- Divisors
- 1, 2, 4, 5, 10, 20
- Sum of divisors
- 42
- Sum without itself
- 22
- Coprime below it
- 8
- Digit sum
- 2
- Digital root
- 2
- Roman numeral
- XX
- Binary
- 10100
- Octal
- 24
- Hexadecimal
- 14
- Base 36
- K
- Bits
- 5 bits
- Collatz steps
- 7 steps · peaks at 20
- Prime before
- 19
- Prime after
- 23
The grid
Ten per row, twenty rows. The filled cells are primes — you can see the multiples of 2 and 5 drop out in columns.
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Numbers either side
How to read this
- The prime factors are what the number is made of. The count and sum of divisors both follow from them.
- Add the divisors, take the number away, and you get perfect, abundant or deficient.
- The length of the binary form is the bit count. 255 taking eight digits is what a byte is.
- Collatz: halve it if even, triple it and add one if odd. The count is how many moves reach 1.
Frequently asked questions
Q. Is 20 a prime number?
No. It breaks down into 2² × 5.
Q. What are the divisors of 20?
1, 2, 4, 5, 10, 20 — 6 divisors in all, adding up to 42.
Q. How is 20 written in binary?
10100, which is 5 bits. In hexadecimal it is 14.
Q. How many Collatz steps does 20 take?
It reaches 1 in 7, peaking at 20 on the way.